1. Field of the Invention
The present invention relates to a process and apparatus for high frequency AC discharge shaping and more particularly to a novel process and apparatus for high frequency AC discharge shaping with improved efficiency and surface treating accuracy and a decreased electrode consumption rate.
2. Description of the Prior Art
It is well-known that a treated surface formed by an electrical discharge shaping operation generally has uneveness somewhat similar to that of a pear, although this disadvantage has been tolerated as a practical matter. For example, in the treatment of a super hard alloy, discharge shaping operations have been performed as a primary treatment and the treated workpiece has been further polished to a mirror finish to remove the surface uneveness caused by the discharge shaping operation. With this polishing treatment, however, it is disadvantageously necessary to spend considerable time and labour in the polishing operation. Other disadvantages of discharge shaping apparatus are the difficulty in electrode feed control and firing, etc.
The voltage applied for conventional discharge shaping operations has been a saw tooth waveform voltage, as shown in FIG. 1, which is generated by a Rutherenco circuit, or the like. However, now it is customary to apply a pulsed voltage as shown in FIGS. 2-4, which is generated by a transistor circuit. FIG. 2 shows a rectangular waveform pulse voltage. FIG. 3 shows a high voltage overlap rectangular waveform pulse voltage and FIG. 4 shows a comb waveform pulse voltage. The illustrated voltage waveforms are all different, however they are similar in that all are single polarity positive or negative pulsating voltages.